1. Field of the Invention
The present invention relates to a method of manufacturing circuit modules and more particularly to a method wherein a connecting material mass is melted prior to an electrode of a component being pressed against the melted mass.
2. Description of the Prior Art
Japanese Patent Application Laid-Open No. 4-314390 discloses a method for mounting an electronic component on a substrate by utilizing a laser beam. Speaking concretely, this patent application discloses a method which loads an electronic component on a substrate so that an external electrode of the component is brought into contact with a cream solder preliminarily applied to a surface of a land and electrically connects the external electrode to the land by way of the solder by irradiating with a laser beam for the cream solder and melting it.
Since this method irradiates the cream solder with the laser beam after the electronic component is loaded on the substrate so that the external electrode of the electronic component is brought into contact with the cream solder preliminarily applied to the surface of the land, it is incapable of directly irradiating the cream solder applied to areas which are sandwiched and shaded by the external electrode and the land.
In other words, this method has a defect that it allows the cream solder to remain unmelted on the areas which are sandwiched and shaded by the external electrode and the land, thereby causing improper connections due to insufficient connecting areas and strengths.
This defect can be corrected to a certain degree by setting an energy (a product of a power multiplied by an irradiation time) of the irradiating laser beam at a high level. When the power of the laser beam is strengthened, however, the electronic component is subjected to bad thermal damage, thereby posing problems of degradation in qualities and variations of characteristics. When the irradiation time of the laser beam is prolonged, on the other hand, each component requires a longer connecting time, thereby making it impossible to accelerate manufacturing of circuit modules.